Drip irrigation systems usually include a continuous irrigation water supply line with separate emitter units installed on the line or in the line, usually at regular intervals. Irrigation water flows through the supply line under pressure, and a small amount of water drips out at the intervals where the drip emitters are installed.
A common approach for controlling drip flow involves use of separate emitter units installed in or on the supply line. The emitter unit receives water flowing in the supply line and passes it through a labyrinth or other passageway that produces a large pressure drop and discharges the water at a uniform drip rate.
Because of life forms in the water flowing through the supply line, especially in waste water systems, slime forms along the inside walls of the tube. As the slime grows, the inner wall loses its smooth surface. Laminar flow within the tube is obstructed by the irregular surface, thereby causing an undesired pressure drop within the tube.
In drip irrigation systems, the growth of the slime also can occur within the emitter unit. Slime grows along the path of the labyrinth and across the outlet hole. As the slime grows within the emitter, the flow of water can be reduced or shut off.
To solve the slime problem, drip irrigation supply lines have been developed containing an anti-bacterial agent for killing the slime-forming bacteria. One example is the subsurface wastewater disposal system from Geoflow, Inc., Corte Madera, Calif. Geoflow's dripline tubing, sold under the mark WASTEFLOW, contains an anti-bacterial interior lining for preventing growth of bacteria on the wall of the tube and preventing undesired buildup of slime on the insides of the tubing and the emitters. This anti-bacterial dripline is described in U.S. Pat. No. 5,332,160 to Ruskin, incorporated herein by reference.
Although the anti-bacterial dripline provides an improvement in reducing the growth of slime on the inside walls of the tubing and the emitters, the present invention provides a further improvement in preventing slime and other bacterial or organic growth from adhering to the inside walls of the tubing and the emitters, especially in wastewater disposal systems where bacterial growth is more of a problem.